FIG. 1 diagrammatically illustrates the overall architecture of a tagged object geolocation system of the type described in the above-referenced Belcher et al Patents, as comprising a plurality of tag emission readers 10 geographically distributed within and/or around an asset management environment 12. This environment contains a plurality of objects/assets 14, whose locations are to be monitored on a continuous basis and reported to an asset management data base 20, which is accessible by way of a computer workstation or personal computer 26. Each of the tag emission readers 10 monitors the asset management environment for RF emissions from one or more RF-transmitter-containing tags 16 that are affixed to the objects 14. Each tag's transmitter is configured to repeatedly transmit or ‘blink’, a very short duration, wideband (spread spectrum) pulse of RF energy, that is encoded with the identification of its associated object and other information that may be stored in a tag memory.
These blinks or bursts of RF energy emitted by the tags are monitored by the readers 10, which are installed at fixed, and relatively unobtrusive locations within and/or around the perimeter of the environment being monitored, such as doorway jams, ceiling support structures, and the like. The output of each tag reader 10 is coupled to an associated reader processor. The reader processor correlates the spread spectrum RF signals received from a tag with a set of spread spectrum reference signal patterns, to determine which spread spectrum signals received by the reader is a first-to-arrive RF spread spectrum signal burst transmitted from the tag.
The first-to-arrive signals extracted by the reader output processors are forwarded to an object location processor within the processing subsystem 24. Using time-of-arrival differentiation of the detected first-to-arrive transmissions, the object location processor executes a prescribed multilateration algorithm to locate (within a prescribed spatial resolution (e.g., on the order of ten feet) the tagged object of interest.
In their normal mode of operation, the tags transmit or ‘blink’ at a relatively slow repetition rate, since most of the objects being tracked do not move frequently. However, there are times when the objects to which the tags are attached are moved and may pass through certain ‘increased sensitivity’ regions of the monitored environment where more frequent tag transmissions are desired, in order to ensure that any objects passing therethrough would be tracked. One way to accomplish this would be to simply program the tags to blink more frequently on a continuous basis.
This approach is not acceptable for two reasons. First, more frequent tag transmissions on a continuous basis will shorten the battery life of the tag; secondly it would increase spectrum congestion. In a similar fashion, there may be regions where changing a tag function is desired, such as stopping the tag from blinking or causing it to start blinking, or to transmit additional data acquired from optional sensors or a data bus.